Electrochemical enhanced heterogeneous activation of peroxymonosulfate by CoFe2O4 nanoparticles to degrade moxifloxacin

The catalytic mechanism of CoFe 2 O 4 nanoparticles (NPs) was investigated in the system of electrochemical enhanced heterogeneous activation of peroxymonosulfate (EC/CoFe 2 O 4 /PMS) with moxifloxacin (MOX) as target contaminant. The removal efficiencies of MOX in PMS, CoFe 2 O 4 , EC, CoFe 2 O 4 /PMS, and EC/CoFe 2 O 4 /PMS system were 18.3%, 36.1%, 43.7%, 96.9%, and 98.3%, respectively. Although there was no synergy effect between EC and heterogeneous catalytic oxidation reaction (HCOR) on MOX removal, the value of apparent rate constant ( k arc ) was much higher in EC/CoFe 2 O 4 /PMS system (0.24 min −1 ) compared with CoFe 2 O 4 /PMS system (0.13 min −1 ). Therefore, EC not only kept the structure of CoFe 2 O 4 NPs stable, but also significantly accelerated the reaction rate of HCOR. Meanwhile, according to electrochemical impedance spectra of catalysts synthesized based on ion-substitution strategy and the EC-HCOR experimental results, the decisive role of Co in PMS activation and the electron transfer between Co and Fe were confirmed. The TOC removal efficiency was reached 74.4% as the ratio of PMS to CoFe 2 O 4 NPs being 0.8 mM to 50 mg/L (30 min), and further improved to 87.6% with batch addition (0.25 mM per 30 min) of PMS (120 min, CoFe 2 O 4  = 100 mg/L). The research results could improve the understanding of catalytic mechanism of spinel oxide in electrochemical system.